The foregoing patents have the same assignee as the instant application and are herein incorporated by reference in their entirety for related and supportive teachings.
1. Field of the Invention
This invention relates to an automobile weight sensor for detecting the presence of a person having a weight in a car seat, and in particular to a sensor that can detect the presence of an occupant using strain sensitive resistors and provide an electrical signal to control activation of an airbag.
2. Description of the Related Art
Various devices are well known for their ability to measure force, pressure, acceleration, temperature, position, etc. by using a sensing structure combined with signal processing electronics. One general type of sensor or transducer for such applications is a resistive strain gauge sensor in which force or pressure is sensed or measured based on strain placed on the resistors. Resistive strain gauges function by exhibiting changes in resistance proportional to force which causes dimensional changes of the resistor. An electrical signal changes voltage level as the resistance changes.
Many types of strain gauge sensors have been designed and made commercially available. Various strain gauge sensors have proven to be generally satisfactory. Prior art sensors, however, have tended to be rather expensive and not suitable in certain applications such as sensing the presence of an occupant in an automobile seat. A sensor suitable for such an application must be compact, robust, impervious to shock and vibration and yet inexpensive.
Automobile seats can use sensors to activate air bags, which would be deployed during an accident. Injury to infants or small children from air bag deployment with excessive force is a current industry problem. A weight sensor in the seat can be used to control the deployment force during air bag activation. If a heavy person is in the seat, the airbag is deployed at full force. If a light person is in the seat, such as a child, the airbag is deployed at a slower, less forceful rate or not at all.
The generated electrical signal does not vary greatly with the weight. As a result the typical electrical signal to be sensed is in the order of millilvolts. When this electrical signal is connected by a wiring harness to an airbag controller, it is sussepetible to noise from cross-talk and coupled electromagnetic interference. This noise can result in an inaccurate weight reading.
A current unmet need exists for a reliable, low cost, simple and robust automobile seat weight sensor that is not affected by noise from cross-talk and coupled electromagnetic interference.
3. Related Art
Examples of patents that are related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 5,573,269 is an apparatus for sensing and restraining an occupant of a vehicle seat.
U.S. Pat. No. 4,556,598 is a porcelain tape for producing porcelainized metal substrates.
It is a feature of the invention to provide a reliable and cost-effective weight sensor and strain gage for detecting weight .
An additional feature of the invention is to provide a weight sensor for measuring a weight applied to the sensor. The sensor includes a substrate having a center section that is adapted to flex in response to the applied weight, at least one step section that is attached to the center section, the center section located adjacent the step section, the step section adapted to concentrate the weight applied thereon onto to the center section and at least one outer section that is attached to the step section. At least one strain gage resistor is mounted on the center section of the substrate for generating an electrical signal in response to the substrate being stressed. At least one wing section is attached to the center section. The wing section is adapted to be out of the path of the weight and not to flex. The wing section contains signal conditioning electronics operative to condition the electrical signal.
The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed and it is distinguished from the prior art in this particular combination of all of its structures for the functions specified. Other features of the present invention will become more clear from the following detailed description of the invention, taken in conjunction with the accompanying drawings and claims, or may be learned by the practice of the invention.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.